winsup/cygwin/init.cc

   1 /* init.cc
   2
   3 This file is part of Cygwin.
   4
   5 This software is a copyrighted work licensed under the terms of the
   6 Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   7 details. */
   8
   9 #include "winsup.h"
  10 #include "cygtls.h"
  11 #include "ntdll.h"
  12 #include "shared_info.h"
  13
  14 static DWORD _my_oldfunc;
  15
  16 static char *search_for  = (char *) cygthread::stub;
  17 unsigned threadfunc_ix[8];
  18
  19 static bool dll_finished_loading;
  20 #define OLDFUNC_OFFSET -1
  21
  22 static void
  23 threadfunc_fe (VOID *arg)
  24 {
  25   _cygtls::call ((DWORD (*)  (void *, void *)) TlsGetValue (_my_oldfunc), arg);
  26 }
  27
  28 /* If possible, redirect the thread entry point to a cygwin routine which
  29    adds tls stuff to the stack. */
  30 static void
  31 munge_threadfunc ()
  32 {
  33   int i;
  34   char **ebp = (char **) __builtin_frame_address (0);
  35   if (!threadfunc_ix[0])
  36     {
  37       char **peb;
  38       char **top = (char **) NtCurrentTeb()->Tib.StackBase;
  39       for (peb = ebp, i = 0; peb < top && i < 7; peb++)
  40         if (*peb == search_for)
  41           threadfunc_ix[i++] = peb - ebp;
  42       if (0 && !threadfunc_ix[0])
  43         {
  44           try_to_debug ();
  45           return;
  46         }
  47     }
  48
  49   if (threadfunc_ix[0])
  50     {
  51       char *threadfunc = NULL;
  52
  53       NtQueryInformationThread (NtCurrentThread (),
  54                                 ThreadQuerySetWin32StartAddress,
  55                                 &threadfunc, sizeof threadfunc, NULL);
  56       if (!search_for || threadfunc == search_for)
  57         {
  58           search_for = NULL;
  59           for (i = 0; threadfunc_ix[i]; i++)
  60             if (!threadfunc || ebp[threadfunc_ix[i]] == threadfunc)
  61                ebp[threadfunc_ix[i]] = (char *) threadfunc_fe;
  62           TlsSetValue (_my_oldfunc, threadfunc);
  63         }
  64     }
  65 }
  66
  67 void dll_crt0_0 ();
  68
  69 /* Non-static fake variable so GCC doesn't second-guess if we *really*
  70    need the alloca'd space in the DLL_PROCESS_ATTACH case below... */
  71 void *alloca_dummy;
  72
  73 extern "C" BOOL
  74 dll_entry (HANDLE h, DWORD reason, void *static_load)
  75 {
  76   BOOL test_stack_marker;
  77
  78   switch (reason)
  79     {
  80     case DLL_PROCESS_ATTACH:
  81       init_console_handler (false);
  82
  83       cygwin_hmodule = (HMODULE) h;
  84       dynamically_loaded = (static_load == NULL);
  85
  86       /* Starting with adding the POSIX-1.2008 per-thread locale functionality,
  87          we need an initalized _REENT area even for the functions called from
  88          dll_crt0_0.  Most importantly, we need the _REENT->_locale pointer
  89          initialized to NULL, so subsequent calls to locale-specific functions
  90          will always fall back to __global_locale, rather then crash due to
  91          _REENT->_locale having an arbitrary value. */
  92       alloca_dummy = alloca (__CYGTLS_PADSIZE__);
  93       ZeroMemory (alloca_dummy, __CYGTLS_PADSIZE__);
  94       memcpy (_REENT, _GLOBAL_REENT, sizeof (struct _reent));
  95
  96       dll_crt0_0 ();
  97       _my_oldfunc = TlsAlloc ();
  98       dll_finished_loading = true;
  99       break;
 100     case DLL_PROCESS_DETACH:
 101       if (dynamically_loaded)
 102         shared_destroy ();
 103       break;
 104     case DLL_THREAD_ATTACH:
 105       if (dll_finished_loading)
 106         munge_threadfunc ();
 107       break;
 108     case DLL_THREAD_DETACH:
 109       if (dll_finished_loading
 110           && (PVOID) &_my_tls > (PVOID) &test_stack_marker
 111           && _my_tls.isinitialized ())
 112         _my_tls.remove (0);
 113       break;
 114     }
 115
 116   return TRUE;
 117 }